Symptoms of a cold usually begin one to two days after catching the virus, whereas the flu symptoms take a little longer to begin (about two to five days). The duration of symptoms is about three days longer in smokers.
Most people are familiar with the symptoms of the common cold. They are usually sore throat, runny nose, sneezing, coughing, congestion and chills. After about one to two days, those symptoms decrease and congestion begins. The symptoms are not always in this pattern, however. Sometimes you can catch a virus that causes a cold but doesn’t yield many symptoms or just very mild ones.
The symptoms can mimic allergy symptoms, and if colds tend to turn into sinus infections or last a long time, the patient should be checked to see if allergies are also causing their symptoms.
Alternately, if a patient has sinus tenderness along with their colds early on, the sinus infection is more likely to be caused by a virus (viral rhinosinusitis) rather than a bacteria, which is typically the cause of a sinus infection.
With infection, patients may also notice a discoloration in their mucus. It is typically clear, but with infection it could be white, yellow or green due to presence of infection-fighting cells. It is important to note that green mucus does not necessarily mean there is a bacterial infection.
The symptoms of the flu are typically respiratory as well. Stomach viruses are different viruses and not considered the flu, even though they are commonly called the stomach flu. In both adults and children, there is abrupt onset of fever, muscle aches and dry cough, with some people also having headache, sore throat and other cold symptoms. The cough symptoms become worse at the end of the illness and can last two to three weeks after the other symptoms are gone. Children may also have additional symptoms of ear infections, nausea and vomiting.
Symptoms typically last five to eight days, but can last longer. Children and those with compromised immune systems (such as diabetics or those on specific medications) tend to be contagious longer.
The virus also causes inflammation and damage in the lungs, particularly with a prolonged cough at the end of the illness. Asthma patients may have an especially tough time with wheezing and coughing.
Some people do not get a fever with the flu, so the lack of fever does not necessarily rule it out. Those people generally either have a milder case or have weakened immune systems. In some cases, both cold and flu viruses affect the brain and cause trouble sleeping.